The present invention is directed to an operation device for an elevator system comprising terminals for connection to a 3-phase AC power source providing a respective AC power supply voltage and a drive device connected to the terminals for driving a motor of the elevator system. More particularly, the invention relates to improvements in an operation device for an elevator system which is designed to operate in normal operation and in an emergency operation of the elevator system.
It is known to provide a source of emergency power for operating elevators when a power source such as a normal building power source fails. The emergency power is supplied, for example, by supplementary generators to provide an auxiliary power supply for running the elevator system in an emergency operation during the power failure. In particular, a suitable operation device which operates the elevator system in an emergency operation must provide a possibility to move the elevator car to a suitable floor when the elevator car stops e.g. between floors because of the power failure.
In U.S. Pat. No. 4,484,664 an emergency drive device for an elevator is described, wherein the elevator operated by an AC motor may be driven in an emergency as during a power supply interruption. During a power supply interruption of a 3-phase power source, the DC output from a rectifier fed to an inverter disappears and an emergency power source becomes operative to supply DC power to the inverter used for converting a constant DC voltage into an AC voltage having desired magnitude and frequency for driving the motor of the elevator system. The emergency power source is connected in series with a diode forming a circuit which is connected across input terminals of the DC/AC inverter. The direct current of the emergency power source is converted into an alternating current of predetermined frequency to drive the elevator motor to cause the elevator car to travel at a lower speed to the nearby floor. In the situation when the car travels down with a heavy load, the kinetic energy is not returned to the DC side, but is consumed at the rotor of the motor. This requires special control logic for controlling the respective transistors of the inverter.
U.S. Pat. No. 5,945,644 A is directed to an apparatus and a method for controlling emergency operation in an elevator system. An auxiliary system is provided to guide an elevator car to the nearest floor for a safe rescue of passengers in case of a stop of the elevator car because of an electrical power failure during operation. The auxiliary system is powered by a battery and serves to convert a direct current voltage of the battery in an alternating current voltage, which is in turn supplied to the elevator system, thereby enabling the passengers aboard the elevator car to be safely rescued. According to a conventional emergency control apparatus described therein, when an emergency situation occurs such as a power failure an emergency power supply is provided by converting the direct current voltage outputted from the battery into a 3-phase alternating current voltage. The converted voltage is provided to a rectifier rectifying the 3-phase alternating current voltage into a direct current voltage which is supplied to an inverter, the inverter converting the received direct current voltage into alternating current voltages for feeding an induction motor. Moreover, the converted 3-phase alternating current voltage of the emergency power supply is provided to a transformer providing a supply voltage to a control circuit for controlling the inverter in the same way as when the supply voltage outputted from the 3-phase power source is provided. The emergency power supply is required to generate a full-swing 3-phase alternating current voltage equal to that of the 3-phase power source.
It is an object of the present invention to provide an operation device for an elevator system which can be integrated into an existing operation device design and which requires only slight circuit modifications.